用eclipse和Tomcat写一个简易聊天室

本文讲述如何用JAVA语言写一个简易的聊天室

简易聊天室的代码实现，因为笔者还是个正在好好学习努力进步的学生，所以代码可能还有很多可以优化的地方，仅供参考。

开发步骤：

第一部分：UI构建
第一步：编写进入页面的静态页面
第二步：编写聊天主页的静态页面
第三步：将进入页面转成动态页面
第四步：将聊天主页转成动态页面
第二部分：功能实现
第一步：编写用户进入聊天室业务逻辑
第二步：实现将用户列表显示
第三步：实现将聊天内容显示
第四步：实现发送聊天内容

用到三大作用域：
HttpServletRequest,HttpSession,ServletContext

效果图如下：

进入界面：

聊天界面：

需要的代码：

InUI.java（进入页面）

public class InUI extends HttpServlet {private static final long serialVersionUID = 2122558975890099050L;@Overrideprotected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {//中文编码支持req.setCharacterEncoding("UTF-8");resp.setCharacterEncoding("UTF-8");//页面输出对象PrintWriter writer = resp.getWriter();writer.println("<html>");writer.println("<head>");writer.println("<meta http-equiv=\"Content-Type\" content=\"text/html; charset=UTF-8\">");writer.println("<title>QG聊天室</title>");writer.println("<style type=\"text/css\">");writer.println("<body background='./ui/g9.jpg' style=\"background-repeat ; background-size:100% 100%   background-attachment:fixed;\">");writer.println("</style>");writer.println("</head>");writer.println("<body>");writer.println("<div style=\"text-align: center; margin: 200px\">");writer.println("<div>");Object msg = req.getAttribute("in_msg");if(msg!=null) {writer.println(msg);}writer.println("<h3>QG聊天室</h3>");writer.println("</div>");writer.println("<div>");writer.println("<form action=\"in.action\" method=\"post\">");writer.println("用户名：<input name=\"username\" size=\"30\"> <input type=\"submit\" value=\"进入\">");writer.println("</form>");writer.println("</div>");writer.println("</div>");writer.println("</body>");writer.println("</html>");}}

MainUI.java

public class MainUI extends HttpServlet {private static final long serialVersionUID = -5468244588883237637L;@Overrideprotected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {req.setCharacterEncoding("UTF-8");resp.setCharacterEncoding("UTF-8");PrintWriter writer = resp.getWriter();writer.println("<html>");writer.println("<head>");writer.println("<meta http-equiv=\"Content-Type\" content=\"text/html; charset=UTF-8\">");writer.println("<title>QG聊天室</title>");writer.println("</head>");writer.println("<frameset cols=\"180,*\">");writer.println("<frame name=\"users\" src=\"users.ui\" noresize=\"noresize\">");writer.println("<frameset rows=\"*,100\">");writer.println("<frame name=\"content\" src=\"content.ui\" noresize=\"noresize\">");writer.println("<frame name=\"message\" src=\"message.ui\">");writer.println("</frameset>");writer.println("</frameset>");writer.println("</html>");}}

ContentUI.java

public class ContentUI extends HttpServlet {private static final long serialVersionUID = 4824128920210671799L;@Overrideprotected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {req.setCharacterEncoding("UTF-8");resp.setCharacterEncoding("UTF-8");HttpSession session = req.getSession();ServletContext context = req.getServletContext();PrintWriter writer = resp.getWriter();writer.println("<html>");writer.println("<head>");writer.println("<meta http-equiv=\"Content-Type\" content=\"text/html; charset=UTF-8\">");writer.println("<meta http-equiv=\"refresh\" content=\"2\">");writer.println("<title>QG聊天室</title>");writer.println("</head>");writer.println("<body>");writer.println("<div>聊天内容</div>");writer.println("<div>");writer.println("<ol>");List<String> contents = (List<String>) context.getAttribute("contents");if(contents!=null) {for(String content:contents) {if(content.contains((String)session.getAttribute("user"))) {writer.println("<li><font color=\"#ff0000\">"+content+"</font></li>");}else {writer.println("<li>"+content+"</li>");}}}writer.println("</ol>");writer.println("</div>");writer.println("</body>");writer.println("</html>");}

MessageUI.java

public class MessageUI extends HttpServlet {private static final long serialVersionUID = 3344260575818484584L;@Overrideprotected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {req.setCharacterEncoding("UTF-8");resp.setCharacterEncoding("UTF-8");PrintWriter writer = resp.getWriter();writer.println("<html>");writer.println("<head>");writer.println("<meta http-equiv=\"Content-Type\" content=\"text/html; charset=UTF-8\">");writer.println("<title>QG聊天室</title>");writer.println("</head>");writer.println("<body>");writer.println("<br />");writer.println("<center>");writer.println("<div>");writer.println("<form action=\"message.action\" method=\"post\">");writer.println("<input name=\"message\" size=\"50\"> <input type=\"submit\" value=\"发送消息\">");writer.println("</form>");writer.println("</div>");writer.println("</center>");writer.println("</body>");writer.println("</html>");}
}

UsersUI.java

public class UsersUI extends HttpServlet {private static final long serialVersionUID = 5378045298264416397L;@Overrideprotected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {req.setCharacterEncoding("UTF-8");resp.setCharacterEncoding("UTF-8");ServletContext context = req.getServletContext();HttpSession session = req.getSession();PrintWriter writer = resp.getWriter();writer.println("<html>");writer.println("<head>");writer.println("<meta http-equiv=\"Content-Type\" content=\"text/html; charset=UTF-8\">");writer.println("<meta http-equiv=\"refresh\" content=\"2\">");writer.println("<title>QG聊天室</title>");writer.println("</head>");writer.println("<body>");writer.println("<div>用户列表</div>");writer.println("<div>");  writer.println("<ul>");List<String> users=(List<String>) context.getAttribute("users");if(users!=null) {for(String username:users) {if(username.equals(session.getAttribute("user"))) {writer.println("<li><font color=\"#ff0000\">"+username+"</font></li>");}else {writer.println("<li>"+username+"</li>");}}}writer.println("</ul>");       writer.println("</div>");writer.println("</body>");writer.println("</html>");}}

InController.java（进入页面的功能实现）

public class InController extends HttpServlet{private static final long serialVersionUID = -7259157146795993735L;@Overrideprotected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {//中文编码req.setCharacterEncoding("UTF-8");resp.setCharacterEncoding("UTF-8");HttpSession session = req.getSession();ServletContext application = req.getServletContext();//获得请求过来的用户名String username = req.getParameter("username");//创建一个集合用于存储用户列表List<String> usernames=(List<String>) application.getAttribute("users");if(usernames==null) {usernames=new ArrayList<>();}boolean flag=false;for(String u:usernames) {if(u.equals(username)) {flag=true;break;}}if(flag==false) {//将用户名放在集合里面usernames.add(username);//将集合放回ServletContext容器里面application.setAttribute("users", usernames);session.setAttribute("user", username);resp.sendRedirect(req.getContextPath()+"/main.ui");}else {req.setAttribute("in_msg", "用户已经存在");req.getRequestDispatcher("/in.ui").forward(req, resp);        }}}

MessageController.java

public class MessageController extends HttpServlet{private static final long serialVersionUID = -8163731608077492143L;@Overrideprotected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {req.setCharacterEncoding("UTF-8");resp.setCharacterEncoding("UTF-8");HttpSession session = req.getSession();ServletContext application = req.getServletContext();String message = req.getParameter("message");List<String> contents=(List<String>) application.getAttribute("contents");if(contents==null) {contents=new ArrayList<>();}String msg="["+session.getAttribute("user")+"]："+message;contents.add(msg);application.setAttribute("contents", contents);resp.sendRedirect(req.getContextPath()+"/message.ui");}}

END

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